The Nuisance of Medusae (Cnidaria, Medusozoa) to Shrimp Trawls in Central Part of Southern Brazilian Bight, from the Perspective of Artisanal Fishermen
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The nuisance of medusae (Cnidaria, Medusozoa) to shrimp trawls in central part of southern Brazilian Bight, from the perspective of artisanal fishermen RENATO M. NAGATA, MARIA A. HADDAD & MIODELI NOGUEIRA JR. Departamento de Zoologia, Universidade Federal do Paraná, Curitiba, PR, Brasil, CEP: 81531-990. Email: [email protected] Abstract. Large aggregations of medusae hinder trawl fishing in coastal waters of several locations worldwide by clogging nets. In Paraná, scyphozoan medusae reach biomass peaks during springtime, when they saturate shrimp trawl nets. In order to assess possible disturbances to trawling caused by species of medusa, 48 fishermen who regularly use fishing trawls from 10 communities in the states of Paraná and Santa Catarina, southern Brazil, were interviewed. The general attitude of the respondents toward jellyfishes was found to be negative. Fishermen associated medusae, particularly the scyphomedusa Lychnorhiza lucerna, with net clogging. Two cubomedusa species, Chiropsalmus quadrumamus and Tamoya haplonema, and the hydromedusa Olindias sambaquiensis were singled out for the painful stings they cause. Large aggregations of medusae in fisheries shorten the duration of trawl hauls, displace hauls to areas further away from the landing ports and prompt fishermen to shift to other fishing gears such as anchored gillnet and drift net, amongst others. The fishermen hold a body of ethnobiological knowledge about jellyfish, such as the identification of toxic species and their seasonal occurrence, and have designed gimmicks to prevent medusae from entering the nets. Key words: Bloom, shrimp, Lychnorhiza lucerna; Olindias sambaquiensis; jellyfish Resumo. O entrave de medusas (Cnidaria, Medusozoa) aos arrastos de camarões na parte central do embaiamento sul do Brasil, pela perspectiva de pescadores artesanais. Ao entupirem redes de arrasto, grandes populações de macromedusas atrapalham a pesca de arrasto em águas costeiras de vários locais do mundo. No Paraná, as macromedusas Scyphozoa, quando atingem os picos de tamanho e biomassa durante a primavera, podem encher completamente redes de arrastos camaroeiros. Para verificar possíveis distúrbios gerados pelas espécies de medusas locais aos arrastos, 48 pescadores atuantes nessa arte de pesca foram entrevistados em 10 comunidades do litoral do Paraná e Santa Catarina. A visão geral dos entrevistados em relação às medusas é negativa. Os pescadores associaram principalmente a cifomedusa Lychnorhiza lucerna ao entupimento de redes. Duas espécies de cubomedusas (Chiropsalmus quadrumamus e Tamoya haplonema) e a hidromedusa Olindias sambaquiensis foram responsabilizadas por dolorosas queimaduras. Grandes agregações de medusas nos locais de pesca diminuem o tempo dos lances de arrastos, deslocam essas operações e causam a evasão para outras artes de pesca como o fundeio e o caceio. Os pescadores detêm um vasto conhecimento etnobiológico sobre as medusas, como o reconhecimento de espécies tóxicas, conhecimento sobre a sazonalidade das ocorrências e artifícios para evitar a entrada de medusas nas redes. Palavras-chave: Floração, camarão sete-barbas, Lychnorhiza lucerna; Olindias sambaquiensis; zooplâncton gelatinoso Introduction world and, occasionally, these animals completely The occurrence of medusa or jellyfish dominate the planktonic biomass (e.g. Pagès et al. (Cnidaria, Medusozoa) in high densities is a 1996, Benovic & Lucic 2001, Mills 2001). Due to common phenomenon in coastal waters around the their large size and the accidents with toxic species, Pan-American Journal of Aquatic Sciences (2009), 4(3): 312-325 The nuisance of medusae to shrimp trawls from the perspective of artisanal fishermen 313 the presence of jellyfish on beaches and shallow on scyphomedusae is yet to be published. It is coastal waters is readily noticed by the public known, however, that macromedusae such the perception (review in Purcell et al. 2001, Haddad Jr. Hydrozoa O. sambaquiensis, the Cubozoa 2002, Purcell et al. 2007, Neves et al. 2007). Chiropsalmus quadrumamus (F. Müller, 1859) and Large medusa aggregations can interfere the three Scyphozoa Lychnorhiza lucerna Haeckel, with fishing activities in two ways: 1) via food 1880, Phyllorhiza punctata von Lendenfeld, 1884 chain, either competing for food with commercial and Chrysaora lactea Eschscholtz, 1829 occur in species (Ishi & Tanaka 2001, Purcell & Sturdvant large numbers in trawl nets, stranded on the beach or 2001, Uye & Ueta 2004; Barz & Hirche 2005) or floating on the water surface (Vannucci, 1951; directly preying upon eggs and larvae of commercial Silveira and Cornelius 2000, Morandini et al. 2005; fishing resources (review in Purcell & Arai 2001); 2) Haddad and Nogueira, 2006; Nogueira and Haddad via clogging of nets, when large numbers of 2006). medusae are caught in a short period, causing On shallow waters (<20 m) of the South stinging accidents (Guest 1959), damaging fishing Brazilian Bight (SBB), small-scale shrimp trawls gear (Brierley et al. 2001) and obstructing or can be filled up with medusae and their biomass displacing local fishing activities (Russell 1970, exceed that of all other animal groups (Graça-Lopes Brodeur et al. 2002, Uye & Ueta 2004; Kawahara et et al. 2002, Branco and Verani 2006). Recent al. 2006a). investigations on the biology of medusae on the Over the last decades, disturbances of coast of Paraná, comprising more than eight years of fishing operations caused by large medusae appear monthly sampling, revealed that short ten-minute to be correlated with recent population increases trawls could catch dozens of kilograms (Fig.1) of the (Brierley et al. 2001, Brodeur et al. 2002, Uye & scyphomedusa L. lucerna, mainly in springtime Ueta 2004; Kawahara et al. 2006a) and/or with the (Nogueira, Haddad and Nagata unpublished data). In introduction of exotic species (Mills, 2001; Galil and the present study, face-to-face interviews with Zenetus 2002; Graham et al. 2003). Such artisanal fishermen from 10 communities of Paraná disturbances may be much more frequent than and north of Santa Catarina were conducted in order reported in the literature, as remarked by Purcell et to ascertain whether such high scyphomedusae al. (2007). biomass represents a nuisance to shrimp trawls. In Brazil, Mianzan and Guerrero (2000) Only Uye & Ueta (2004) used the same method to reported high biomass of the large hidrozoans report fishery losses caused by gelatinous plankton. Olindias sambaquiensis F. Müller, 1861 and Based on a fishermen poll, these authors analyzed Rhacostoma atlantica L. Agassiz, 1850, in Cabo de the increase of Aurelia aurita populations in the Santa Marta upwelling (28ºS), but quantitative data Island Sea of Japan during the last 20 years. Figure 1. Catch of a small-scale shrimp trawl haul of 15 minutes, with abundance of Lychnorhiza lucerna in Paraná coast, Brazil. Courtesy of Cláudio D. Natividade. Pan-American Journal of Aquatic Sciences (2009), 4(3): 312-325 314 R. M. NAGATA ET AL. Despite increased attention given to medusa developed along the Southern Brazilian Bight disturbances to fishing worldwide (e.g. Mills 2001, (SBB), reaching 175 to 190 km width. Along the Kawahara et al. 2006a, Purcell et al. 2007) and the coastline of the States of Paraná and Santa Catarina, great abundance of jellyfish on the Brazilian coast, between the beaches of Pontal do Sul and Itapema which can potentially interfere with fishing do Norte – SC (Fig. 2), local fishermen target more operations, no study has investigated the social and than 70 species of fish and shellfish. The main commercial impacts in Brazil. This paper also fishing resource in the area, however, is the sea-bob documents, for the first time, information on shrimp Xiphopenaeus kroyeri Heller, 1862, caught fishermen’s ethnobiological knowledge concerning primarily by bottom trawling carried out by small these gelatinous animals. trawling vessels (Natividade et al. 2004). This practice is limited to ca. 20 km off shore, where Material and Methods depths are 6 meters in average. (Andriguetto-Filho et Study Site. The continental shelf is well al. 2006). Figure 2. Site of interviewed fishing communities on Paraná and Santa Catarina states. 1- Pontal do Sul; 2 – Atami; 3– Barranco;4- Shangrilá; 5– Ipanema; 6– Praia de Leste; 7- Caieiras; 8- Brejatuba; 9- Barra do Saí; 10- Itapema do Norte. Data Collection. Standardized time wasted when trawling results in massive questionnaires and open interviews (Table I) were jellyfish captures. When answers to the given to 48 trawl fishermen active in 10 questionnaire suggested the presence of large communities of Paraná and northern Santa Catarina medusae concentrations in the trawls, the following (Fig. 2), over given periods from 2003 to 2004 and information was also gathered: A) references to from 2006 to 2007. The following information was jellyfish as a nuisance to trawls; B) reports of asked in the questionnaire: I) age of the fisherman; accidents caused by toxic species; and C) whether II) time of experience on fishing activities; III) time of hauls was shortened in periods of large whether trawling gear is used exclusively or not; IV) jellyfish abundance. whether they report economic losses caused by For the category of open interviews, 20 local jellyfish; V) whether large numbers of jellyfish expert fishermen, very experienced in the practice of cause an impediment to trawling; and VI) amount of trawl fishing, were recommended by researchers and Pan-American Journal of Aquatic Sciences (2009), 4(3):